When does a person actually die? I know it seems like a silly question, Norbert. Most people assume it's when the heart stops but it turns out genes not only continue to work hours after death, but some genes actually turn on upon death.

A new study looked at messenger RNA which are used by genes to tell cells which proteins to produce. The more messenger RNA there is, the more active the gene. In zebra fish and mice, there was gene activity from half an hour up to 96 hours after death. In fact, scientists found over a thousand genes were significantly active up to four days post mortem. Some not only turned on, they ramped up including genes involved in stress, immunity, inflammation, embryogenesis and cancer. Many of these genes seemed to be trying to keep the body going. It would be like a car engine trying to restart itself without any gas.

Since the study worked on two very different organisms, a fish and a mouse, and yet found similar genes activated upon death, these genes may be specific to death and could be turned on as well in us when we die. What researchers also found is that in death certain genes that had been turned off while the animal was a developing fetus were now turned on. It suggests the body could no longer control these genes and left uncontrolled would have led to rapid growth and cancer.

The study has several practical uses, for one, it can help forensic scientists tell the precise time of death. We may also better understand whether transplanted organs are susceptible to cancer due to the activation of embryonic genes.

If you're worried this will lead us to zombies' no chance. For now all we have are zombie genes.